The present invention relates to a hard disk drive used as an external memory device for a computer, and more particularly, to an assembly for maintaining an actuator of a hard disk drive in a parking zone while the actuator is not in operation.
Typically, and as is illustrated in Bistable Magnetic/Electromagnetic Latch For A Disk File Actuator by J. Lindsay, et al., U.S. Pat. No. 5,208,713 and in Rotary Internal Latch For Disk Drive Actuator To Protect Against Rotational Shock Force, by J. H. Morehouse, et at., U.S. Pat. No. 5,296,986, a disk drive in a computer includes a disk which is rotated at a high speed by a spindle motor, and an actuator for initiating movement of a magnetic head that reads and writes data recorded on tracks of the disk. The actuator has a cantilevered arm that is mounted upon a pivot positioned at a first end, enabling access of the magnetic head to substantially the entire base surface of the disk. A bobbin and a coil, installed at the first end of the actuator, move the arm of the actuator through operation of a voice coil motor. Head gimbals, connected to a second, or distal end of the arm of the actuator, act as a conduit between the actuator and the magnetic head. The magnetic head, installed on a front portion of the head gimbals, positions itself along the surface of the disk, thereby writing and reading data to and from the disk tracks as the disk rotates. When the disk drive is started, the disk rotates and the airflow accompanying this rotation causes the magnetic head to float up from the surface of the disk, and drives it to access the disk for recording or read-out of data, and when the disk drive is halted the magnetic head comes to rest at a parking zone.
Upon de-energization of the disk drive, the actuator is placed in a locked state and the magnetic head is accordingly positioned in a parking zone located on an inner portion of the disk, thereby preventing recorded data from being damaged due to undesired contact of the magnetic head against the surface of the disk, a contact that might deleteriously permanently impair the ability of the disk to receive and maintain storage of data as bits of magnetic data.
In the design of disk drives, it is therefore imperative that an actuator device, such as the aforementioned examples, provide a reliable locking mechanism by which the device itself, and the magnetic head that it controls, will be positionally secured in order to prevent undesired movements which could disrupt or destroy the recorded data. Accordingly, many types of locking mechanisms for actuator arms have emerged.
One type of actuator locking mechanism utilizes permanent magnets. While magnet-type locking mechanisms are generally desirable, having many advantages over manual locks which require the intervention of an informed user, they are also known to have certain disadvantages associated with them. For example, most magnet-type locking mechanisms require that a portion of the actuator be placed in direct contact with a locking magnet. I have observed that this type of mechanism unfortunately has the adverse affect of converting kinetic energy produced from the activator into undesired, extraneous noise signals.
Even if a locking mechanism is designed to avoid occurrence of direct contact between the actuator and the locking magnet, adverse effects can still result from the mere presence of a magnetic field in proximity with the actuator. Specifically, when the magnectic head is positioned around the track on which the innermost data is recorded, the magnetic field can result in undesired forces being applied to the actuator, thereby adversely affecting the servo-control functions of the drive, lengthening the read time, and increasing the probability of data errors.